Recyclable cross-linked diene elastomers comprising furanyl groups and precursors thereof

ABSTRACT

Disclosed are new precursors of recyclable cross-linked diene elastomers including chain-end units with furanyl groups, their use in the preparation of the recyclable elastomers and their process of preparation. Also disclosed are new recyclable cross-linked diene elastomers, their preparation process and their uses.

The present invention concerns new precursors of recyclable cross-linkeddiene elastomers, their use in the preparation of said recyclableelastomers and their process of preparation. The invention also concernsnew recyclable cross-linked diene elastomers, their preparation processand their uses.

In 2015, the total rubber production was over 26 millions of tons.Natural and synthetic rubbers like polyisoprene,polyethylene/propylene/diene (EPDM) or polybutadiene (PB) are widelyused in many areas like automotive, sport equipment, building materialsor tires. Their elasticity, strength, high moduli or solvent resistanceare the main properties expected for these materials. To reach theseproperties, the rubber has to be chemically cross-linked. Sulfurvulcanization and peroxide curing are currently the main methods used inindustry. However, the network produced by these pathways isirreversibly cross-linked. As a consequence, the material cannot becorrectly recycled and leads to important quantities of wastes.

Recently, new routes to synthesize reversible cross-linked materialswere investigated. Among reversible reactions, the Diels-Aider (DA)reaction has already been tested on a wide range of polymers likepolyurethane, epoxy or recently on polybutadiene to create reversiblenetwork. One of the most popular DA reaction involves a furan and amaleimide leading to an adduct that can dissociate under thermaltreatment with few side reactions in mild reaction conditions.

The thiol-ene reaction is used to graft furanyl groups along apolybutadiene chain. The bis-maleimide, used as the cross-linking agent,is then added to the modified elastomer to form a thermosensitivedynamic network. However, several disadvantages have to be consideredwith the thiol-ene reaction: some side reactions like cyclization oruncontrolled cross-linking can occur. Moreover, the molar mass of thepolybutadiene used is high, comprised between 135 and 200 kg·mol⁻¹,increasing solubilization time, washing steps and complicating chemicalcharacterization or molding due to this high viscosity.

There is thus a need to provide new precursors for the preparation ofrecyclable cross-linked diene elastomers and new recyclable cross-linkeddiene elastomers thereof. In particular, there is a need to provideprecursors of recyclable cross-linked diene elastomers which can beeasily and efficiently obtained and used in the industry, and especiallyhaving a low viscosity.

The aim of the present invention is to provide new compounds, inparticular useful as precursors for the preparation of recyclablecross-linked diene elastomers.

A particular aim of the invention is to provide precursors for thepreparation of recyclable cross-linked diene elastomers having a lowviscosity and which are easy to use in said preparation process.

An aim of the invention is to provide a process of preparation of suchprecursors.

Another aim of the invention is to provide new recyclable cross-linkeddiene elastomers, in particular recyclable polybutadiene, polyisoprene,and polychloroprene.

A particular aim of the invention is to provide new thermoreversiblecross-linked to diene elastomers.

Another aim of the invention is to provide a process of preparation ofsaid recyclable cross-linked diene elastomers.

The present invention thus concerns a compound having the followingformula (I):

-   -   wherein:        -   n is an integer comprised between 10 and 2 000, preferably            between 15 and 1 500;        -   R_(a) is selected from the group consisting of: H, linear or            branched (C₁-C₅)alkyl, and halogen atom;        -   A comprises at least one repeating unit (U) having the            formula (U1) or (U2):

-   -   -   with R_(a) being as defined above and R_(a″) being selected            from the group consisting of H, —CH—CH₂, and            —C(═CH₂)(R_(a)), R_(a) being as defined above;        -   B₁ and B₂, independently of each other, have the following            formula (B):

-   -   or the following formula (C):

-   -   wherein at least one of B₁ and B₂ has the formula (B),        and wherein:    -   —X is:        -   a bond or        -   a group of formula —NH—X₁—, wherein X₁ is a linear or            branched (C₁-C₅)alkylene group;    -   Y is selected from the linear and branched (C₁-C₅)alkylene        groups;    -   Z and Z′ are independently of each other —O— or —NH—;    -   W and W′ are independently of each other selected from the group        consisting of: —C(═O)—NH—Y′—, —C(═O)—Y′—, and —Y′— groups, Y′        representing a linear or branched (C₁-C₅)alkylene group,        preferably a (C₁-C₃)alkylene group.

The present inventors surprisingly synthesized well-definedthermoreversible cross-linked diene elastomers by using easy andefficient chemistry for chain-ends modifications, in particular by usingchain-ends units comprising furanyl groups in their precursors.

More particularly, the inventors discovered new precursors of saidelastomers by first degrading commercial high molar mass dieneelastomers into polymers with lower molar masses, leading to asignificant decrease of the viscosity of the polymers. For example, themolar mass of the degraded commercial elastomers, in particular ofdegraded commercial polybutadiene, ranges to from 1 000 g·mol⁻¹ to 50000 g·mol⁻¹, preferably from 1 000 g·mol⁻¹ to 25 000 g·mol⁻¹, and moreparticularly from 5 000 g·mol⁻¹ to 20 000 g·mol⁻¹.

From these polymers, furanyl telechelic precursors were prepared, withvarious chain lengths. The addition of a cross-linking agent to theseprecursors surprisingly yields to various cross-linked diene elastomers.

According to the invention, the cross-linking is thermoreversible: thediene elastomers of the invention are in particular usable in atemperature range comprised between −70° C. and +80° C., preferablybetween −40° C. and +80° C. without losing their mechanical properties.

Moreover, the cross-linked diene elastomers of the inventionsurprisingly keep their mechanical properties after several remoldingcycles, for example after 1 to 5 cycles of remolding.

The present inventors also surprisingly discovered that higher chainlength of the precursors of the invention, for example with n as definedabove being comprised between 300 and 500, reduces the Young and elasticmoduli with high elongation at break, whereas shorter chain length ofthe precursors, for example with n as defined above being comprisedbetween 30 and 80, reduces the elongation at break but increases theYoung and elastic moduli.

Lastly, it was discovered that the mechanical properties of the dieneelastomers network can be tuned by monitoring the quantity of thecross-linking agent used in their preparation process.

Definitions

By “mechanical properties”, it may be meant the elasticity, inparticular characterized by the elastic modulus and the loss modulus,the young modulus, the maximum stress at break and the maximum strain atbreak.

By “low viscosity”, it is meant a viscosity comprised between 0.1 and3000 Pa·s.

The term “(C₁-C₅)alkyl” means a saturated aliphatic hydrocarbon groupwhich may be straight or branched having from 1 to 5 carbon atoms in thechain (i.e. an alkane missing one hydrogen atom).

The term “(C₁-C₁₀)alkyl” means a saturated aliphatic hydrocarbon groupwhich may be straight or branched having from 1 to 10 carbon atoms inthe chain (i.e. an alkane missing one hydrogen atom).

Preferred alkyl groups are methyl, ethyl, propyl or isopropyl groups,more particularly methyl groups. “Branched” means that one or loweralkyl groups such as methyl, ethyl or propyl are attached to a linearalkyl chain.

The term “(C₁-C₅)alkylene” means a saturated aliphatic hydrocarbondivalent group which may be straight or branched having from 1 to 5carbon atoms in the chain (i.e. an alkane missing two hydrogen atoms).

The term “(C₁-C₂₀)alkylene” means a saturated aliphatic hydrocarbondivalent group which may be straight or branched having from 1 to 20carbon atoms in the chain. (i.e. an alkane missing two hydrogen atoms).

Preferred alkylene groups are methylene, ethylene or propylene groups.“Branched” means that one or lower alkylene groups such as methylene,ethylene or propylene are attached to a linear alkylene chain.

By “(C₃-C₆)cycloalkyl” is meant a cyclic, saturated hydrocarbon grouphaving 3 to 6 carbon atoms, wherein any ring atom capable ofsubstitution may be substituted by a substituent. Preferred cycloakylgroups are cyclopropyl or cyclobutanyl groups, preferably notsubstituted.

The term “3-6 membered heterocyclyl” refers to a saturated monocyclichydrocarbon ring system comprising from 3 to 6 carbon atoms, wherein anyring atom capable of substitution may be substituted by a substituent,for example (═O) or ClSO₂, and wherein one or more carbon atom(s) arereplaced by one or more heteroatom(s) such as nitrogen atom(s), oxygenatom(s) and sulfur atom(s); for example 1 or 2 nitrogen atom(s), 1 or 2oxygen atom(s), 1 or 2 sulfur atom(s) or a combination of differentheteroatoms such as 1 nitrogen atom and 1 oxygen atom. Preferredheterocyclyl groups are epoxydyl, azetidinyl and dihydrofuran-2,5-dionylgroups. More particularly, the heterocyclyl group is an epoxydyl group.

By a “trivalent linear or branched (C₁-C₁₀)alkane” is meant a saturatedaliphatic hydrocarbon group having from 1 to 10 carbon atoms and missingthree hydrogen atoms, with the terms “linear” or “branched” as definedfor the alkyl groups. For example, R′ is a trivalent (C₁-C₁₀)alkane informula (VIII) and is thus an alkane linked to the three nitrogen atomsof formula (VIII).

By a “trivalent (C₆-C₁₀)arene”, is meant an aromatic monocyclic,bicyclic, or tricyclic hydrocarbon ring system comprising from 6 to 10carbon atoms and missing three hydrogen atoms. For example, R′ is atrivalent (C₆-C₁₀)arene in formula (VIII) and is thus an arene linked tothe three nitrogen atoms of the compounds of formula (VIII).

The term “halogen” refers to the atoms of the group 17 of the periodictable and includes in particular fluorine, chlorine, bromine, and iodineatoms, more preferably fluorine, chlorine and bromine atoms. In aparticular embodiment, the halogen is the chlorine atom.

All diastereoisomeric forms (cis and trans; Z and E) and all geometricisomeric forms of the compounds and polymers of the invention areintended, unless the diastereoisomeric or the isomeric form isspecifically indicated.

Precursors of General Formula (I)

By “precursors”, “precursors of the invention” or “precursors of therecyclable cross-linked diene elastomers”, it is meant compounds offormula (I) as described above.

In one embodiment, the precursors of formula (I) do not comprise asulfur atom.

According to one embodiment, the precursors of formula (I) comprise atleast two repeating units (U). In one preferred embodiment, A consistsof repeating units (U). In one embodiment, the repeating units (U) areidentical. In another embodiment, A comprises at least one unit (U1) andat least one unit (U2), preferably A consists of repeating units (U1)and (U2). In another embodiment, A comprises at least two units (U1) andat least two units (U2).

In one embodiment, the repeating unit (U) is of formula (U1):

with R_(a) as defined above.

In another embodiment, the repeating units (U) are selected from thegroup consisting of:

R_(a) being as defined above, and wherein (U′) and (U″) correspondrespectively to the cis and trans isomers of formula (U1).

In one embodiment, when X is a bond, then Z is —O—, and when X is—NH—X₁—, then Z is —NH—.

In another embodiment, B₁ is of formula (B) as defined above and B₂ iseither of formula (B) or of formula (C) as defined above.

In one embodiment, Z and Z′ are identical and W and W′ are alsoidentical (in this case, one of B₁ and B₂ is of formula (B) and theother is of formula (C).

In one embodiment, A further comprises at least one repeating unit (V)having the following formula:

-   -   wherein:        -   R_(b) is selected from the group consisting of: H, OH,            (C₁-C₅)alkyl, and halogen atom;        -   R_(c) is H or an halogen atom, or R_(b) and R_(c) form            together with the carbon atom carrying them a —C═CH₂ group;        -   R_(d) is selected from the group consisting of: H, OH,            —S—C(═O)—R_(g), —S—C(—S)—R_(g), —P(—O)(OR_(g))₂, —B(R_(g))₂,            dihydrofuran-2,5-dionyl, and CX′₂R_(f),            -   X′ being a halogen atom,            -   R_(f) being selected from the group consisting of                halogen atom, CH₃—C(═O)—O—(C₁-C₁₀)alkyl, —P(═O)(Hal)₂                with Hal being an halogen atom,            -   R_(g) being a linear or branched (C₁-C₁₀)alkyl group,    -   or R_(c) and R_(d) form together with the carbon atoms carrying        them a (C₃-C₆)cycloalkyl or a 3-6 membered heterocyclyl group,        said cycloalkyl and heterocyclyl groups being optionally        substituted;        the percentage of the number of repeating units (V) being        inferior or equal to 80% of the number of repeating units (U),        preferably inferior or equal to 50% of the number of repeating        units (U).

By “optionally substituted”, it may be meant that said cycloalkyl andheterocyclyl groups are optionally substituted by one or moresubstituent(s) selected from the group consisting of: (C₁-C₅)alkyl,halogen atom, (═O) and —SO₂Cl, preferably (═O) and —SO₂Cl.

In one embodiment, Rb is H or OH, Rc is H and Rd is H or OH; or R_(c)and R_(d) form together with the carbon atoms carrying them an oxiranegroup.

In one embodiment, the percentage of the number of repeating units (V)is inferior or equal to 10%, based on the number of repeating units (U).

In a particular embodiment, the repeating units (V) are identical andare preferably selected from the group consisting of:

wherein R_(b), X′, R_(f), and R_(g) are as defined above.

In one particular embodiment, the repeating units (V) are identical andare selected from (V4), (V7), and (V8), with R_(b) and R_(g) as definedabove. In a preferred embodiment, the repeating units (V) are of formula(V4), with R_(b) as defined above, preferably with R_(b) being H.

In one embodiment, A consists of repeating units (U) or consists ofrepeating units (U) and (V) as defined above. In one embodiment, when Afurther comprises at least one repeating unit (V), then the repeatingunits (U) are of formula (U1).

In one embodiment, R_(a) is H or a (C₁-C₅)alkyl group, preferably R_(a)is H or CH₃. In a particular embodiment, R_(a) is H. In one embodiment,R_(a′) is H.

In one embodiment, Z is —O— and W is —C(═O)—NH—Y′—, Y′ being preferablya —CH₂— group. In one embodiment, Z′ is —O— and W′ is —C(═O)—NH—Y′—, Y′being preferably a —CH₂— group.

In one embodiment, W is —C(═O)—NH—Y′, Y′ being preferably a —CH₂— group.

In one embodiment, X is a bond or a —NH—(CH₂)₂— group, preferably abond.

In one embodiment, Y is a —(CH₂)₂—, —(CH₂)₃— or a —CH₂—CH(CH₃)— group,preferably a —(CH₂)₂— group.

In a particular embodiment, the compound of formula (I) has thefollowing formula (Ia):

wherein n, R_(a), A, X, Y, Z and W are as defined herein. PreferablyR_(a) is H, CH₃ or Cl.

The compound of formula (Ia) corresponds to a compound of formula (I)wherein B₁ and B₂ are of formula (B).

The invention also concerns compounds having one of the followingformulae:

-   -   wherein n is as defined above.        Process for the Preparation of the Precursors of General Formula        (I)

The invention also relates to a process for the preparation of acompound of formula (I), in particular when the repeating units have theformula (U1), as defined above, comprising the following steps:

-   -   a) a reductive amination step comprising the reaction of an        aldehyde of formula (II):

with at least one amine of formula (III):

-   -   with n, R_(a), A, X, Y, and Z being as defined above,    -   in order to obtain a compound having the following formula (IV):

-   -   with n, R_(a) and A being as defined above, and    -   wherein B₁′ and B₂′, independently of each other, have the        formula (B′):

-   -   or form with the carbon atom carrying them a —C═O group,    -   and wherein at least one of B₁′ and B₂′ is of formula (B′);    -   b) optionally, if one of B₁′ and B₂′ forms with the carbon atom        carrying it a —C═O group, a reduction step comprising the        reaction of the compound of formula (IV) as defined above with a        reducing agent, for example NaBH₄, in order to obtain a compound        having the formula (IV′):

-   -   -   with n, R_(a) and A being as defined above, and        -   wherein B₁″ and B₂″, independently of each other, have the            formula (B′):

-   -   -   or —OH,        -   and wherein at least one of B₁″ and B₂″ is of formula (B′);

    -   c) the reaction of the compound of formula (IV) or (IV) with at        least one functionalized furane having the following formula        (VI):

-   -   -   wherein W″ is independently chosen from the group consisting            of: —Y—N═C═O, —Y′—C(═O)—Cl, —Y′—C(═O)—OH, —Y′—C(═O), and            —Y′-Hal, Y′ being as defined above and Hal being an halogen            atom;        -   in order to obtain a compound having the formula (I).

In a particular embodiment, the reductive amination step a) comprisesthe reaction of an aldehyde of formula (II):

with two amines of formula (III):

-   -   n, R_(a), A, X, Y, and Z being as defined above,    -   in order to obtain a compound having the following formula        (IVa):

-   -   -   then, the reaction of the compound of formula (IVa) with            four functionalized furane groups having the following            formula (VI):

-   -   wherein W″ is independently chosen from the group consisting of:        —Y′—N═C═O, —Y′—C(═O)—Cl,    -   —Y′—C(═O)—OH, —Y′—C(═O), and —Y′-Hal, Y′ being as defined above        and Hal being an halogen atom;    -   leads to a compound having the formula (Ia).

Advantageously, the aldehyde of formula (II) according to the inventionmay be obtained by a degradation step of commercial polymers, inparticular polymers having a high molar mass, for example comprisedbetween 100 000 and 500 000 g·mol⁻¹. Among these commercial polymers, itmay be cited the polybutadiene, the polyisoprene or the polychloroprene.This degradation step is well-known in the art. For example, thedegradation step may be performed by an epoxidation step of saidcommercial polymers, followed by a cleavage of the oxirane groups, inparticular by periodic acid.

The operating conditions of the above-mentioned steps a), b) and c) areknown in the art.

The reductive amination (step a)) may be performed in the presence of anorganic solvent such as tetrahydrofurane, dichloromethane,dichloroethane, tetrachloroethane, chloroform, toluene, diethyl ether,ethyl acetate, cyclohexane, or their mixtures; preferablytetrahydrofurane. The reductive amination (step a)) may be performed attemperature range of −20° C. to 50° C., more particularly at a range of20 to 25° C.

The addition of the functionalized furane (step c)) may be performed inthe presence of an organic solvent such as dichloromethane,dichloroethane, tetrachloroethane, chloroform, toluene, diethyl ether,ethyl acetate, cyclohexane, or their mixtures; preferablytetrahydrofurane.

The addition of the functionalized furane (step c)) may be performed ata temperature range of −20° C. to 50° C., more particularly at a rangeof 25 to 35° C. In one embodiment, it is performed in the presence of acatalyst such as dibutyltindilaurate, preferably in a molar ratio of0.1% to 10% compared to the compound VI for example in a range of 2% to5%.

The above-mentioned steps a) and c) may be performed at a temperaturecomprised between 20° C. and 60° C., for example about 40° C.,preferably under inert atmosphere.

In one embodiment, some of the units (U1) may be later functionalizedaccording to known methods, to obtain the precursors of formula (I)and/or the polymers of the invention comprising the units (V) as definedabove.

The invention further relates to a compound having the following formula(IV):

wherein n, R_(a), A, B₁′ and B₂′ are as defined above.

The compounds of formula (IV) are intermediate compounds in thepreparation of the precursors of formula (I).

In one embodiment, said compound of formula (IV) has the followingformula:

wherein A, n and Z are as defined above.Polymers Obtained from the Precursors of General Formula (I)

The invention relates to a polymer, preferably a recyclable polymer,susceptible to be obtained by the reaction of a compound of formula (I)as defined above, with a crosslinking agent comprising at least twomaleimidyl groups.

In a particular embodiment, the ratio cross-linking agent/precursors offormula (I) is comprised between 0.1 and 1, preferentially between 0.5and 1.

In one embodiment, the crosslinking agent has the following formula(VII):

-   -   wherein R is chosen from the group consisting of:        -   a linear or branched (C₁-C₂₀)alkylene, said alkylene being            optionally interrupted by one or more heteroatom(s), such as            O or S;        -   a phenylene, said phenylene being optionally substituted by            one or more substituent(s) selected from (C₁-C₁₀)alkyl,            preferably by one or more methyl group(s); and    -   a phenylene-L-phenylene group, with L being selected from the        group consisting of: a bond, a (C₁-C₆)alkylene, —O— and —SO₂—.

In a particular embodiment, the crosslinking agent is selected from thegroup consisting of: 1,1′-(methylenedi-4,1-phenylene)bismaleimide,N,N′-(4-methyl-1,3-phenylene)bismaleimide,1,1′-(3,3′-dimethyl-1,1′-bisphenyl-4,4′diyl)bismaleimide,N,N′,-(1,3-phenylene)bismaleimide, N,N′,-(1,4-phenylene)bismaleimide,N,N′-(1,2-phenylene)bismaleimide, dithio-bis-maleimidoethane,1,11-bismaleimido-triethyleneglycol,4,4′-oxybis(methylbenzene)bismaleimide.

Preferably, said crosslinking agent is the1,1′-(methylenedi-4,1-phenylene)bismaleimide, having the followingformula:

According to an embodiment, the crosslinking agent has the followingformula (VIII):

wherein R′ is chosen from the group consisting of: a trivalent(C₁-C₁₀)alkane, or a trivalent (C₆-C₁₀)arene, preferably a trivalentmethane or a trivalent benzene.

The present invention also relates to a process of preparation of apolymer comprising the reaction of a compound of formula (I) as definedabove, with a crosslinking agent comprising at least two maleimidylgroups as defined above. The invention relates to a polymer obtained bysaid process of preparation. The invention relates to the use of thecompound of formula (I), for the preparation of a polymer.

In particular, the polymers of the invention are elastomers, preferablyrecyclable elastomers. Indeed, said elastomers can undergo from 1 to 5remolding cycles without any loss of their mechanical properties.

The remolding step can be performed by the dissolution of said elastomerin an organic solvent such as chloroform, dichloroethane,tetrachloroethane, toluene, tetrahydrofurane, preferably chloroform. Inone embodiment, said remolding step is performed at a temperaturecomprised between 100° C. and 150° C., for example comprised between110° C. and 130° C., such as 120° C.

The invention also relates to the use of the polymers and/or elastomersas defined above in tires, rubber seals, automotives, and buildings. Inparticular embodiment, said polymers and/or elastomers as defined abovemay be used in a temperature range comprised between −70° C. and +80°C., preferably between −40° C. and +80° C.

DESCRIPTION OF THE FIGURES

FIG. 1A: ¹H NMR spectrum of the aldehyde telechelic polybutadiene offormula (II).

FIG. 1B: ¹H NMR spectrum of the hydroxyl telechelic polybutadiene offormula (IV).

FIG. 1C: ¹H NMR spectrum of the furan telechelic polybutadiene offormula (I) for the 5 000 g·mol⁻¹ series in CDCl₃.

FIG. 2: SEC chromatograms of the synthetic intermediates for the 9 000g·mol⁻¹ series: PBAT (aldehyde of formula (II)); PB—OH₄ (compound offormula (IV)); and PB-fur4 (precursor of formula (I)).

FIG. 3: Photo of a remolding cycle.

FIG. 4A: Normalized DSC curves comparison of the cross-linked PB series.The two endothermic peaks at 110° C. and 140° C. represent the retroDAof the exo and endo adducts respectively, exothermic peak at 160° C.represents the homopolymerisation of the bis-maleimide.

FIG. 4B: Normalized DSC curves comparison of the 9 000 g·mol⁻¹modification series showing the melting peak decreases at −8° C. withthe chain-end modifications.

FIG. 5A: TGA curves comparison of the cross-linked PB series showing theincreases loss mass at 300° C. due to the furan content.

FIG. 5B: TGA curves comparison of the 9 000 g·mol⁻¹ modification seriesshowing that the weight loss at 300° C. is related to the furanpresence.

FIG. 6A: DMTA analysis of the cross-linked PB, effect of the chainlength on the rubbery plateau (E′).

FIG. 6B: DMTA analysis of the cross-linked PB, effect of the chainlength on the lost modulus (δ).

FIG. 7: Young's modulus comparison of the cross-linked PB between thefirst molding (solid lines) and the recycled ones (dashed lines).

FIG. 8: DMA curves obtained after 5 reprocessing of the reversiblecross-linked polybutadiene.

FIG. 9: Effect on the tensile test analysis after 5 reprocessing of thereversible cross-linked polybutadiene.

FIG. 10: Effect of the Bis-maleimide quantity on the mechanicalproperties of the network analyzed in DMA.

FIG. 11: Effect of the Bis-maleimide quantity on the mechanicalproperties of the network analyzed in tensile test.

EXAMPLES Example 1: Synthesis of Precursors of Formula (I) According tothe Invention

The compound 4, corresponding to a precursor of formula (I) of theinvention, is prepared according to the following scheme 1:

1.1. Materials

Cis-1,4-polybutadiene (1, cis-1,4-PB, 98% cis-1,4, M_(n)=150 kg·mol⁻¹,Ð=2.8) was purchased from Scientific Polymer Products, Inc.3-Chloroperoxybenzoic acid (mCPBA, 70-75%, Acros), periodic acid (H₅IO₆,≥99%, Aldrich), acetic acid (99%, Aldrich), sodium triacetoxyborohydride(NaBH(OAc)₃, 97%, Aldrich), diethanolamine (DEA, 99%, Alfa Aesar),furfuryl isocyanate (Furan-NCO, 97%, Aldrich),1,1′-(methylenedi-4,1-phenylene)bismaleimide (Bismaleimide, 95%, AlfaAesar), celite 545 (VWR), dibutyltin dilaurate (DBTDL, 95%, TCI) wereused without further purification. Tetrahydrofuran (THF) anddichloromethane (DCM) were dried on alumina column. Chloroform (CHCl₃),methanol and diethyl ether (reagent grade, Aldrich) were used asreceived.

1.2. Polybutadiene Chemical Modifications

1.2.1. Synthesis of Aldehyde Telechelic Cis-1,4-polybutadiene (2, ATPB),Compound of Formula (II) of the Invention

High molar mass cis-1,4-polybutadiene 1 was first epoxidized with agiven molar ratio of mCPBA/butadiene (BD) units, followed by subsequentone-pot cleavage of oxirane units by adding periodic acid as describedin the literature. A typical reaction procedure is as follows. mCPBA(300 mg, 1.25 mmol) dissolved in 10 mL of THF was added dropwise to asolution of cis-1,4-polybutadiene (3.22 g, 59.6 mmol of BD units) in 80mL of THF at 0° C. After 2 h of reaction at room temperature, periodicacid (1.05 eq. compared to mCPBA, 342 mg) dissolved in 10 mL of THF wereadded dropwise and stirred during 2 h at room temperature. The solventwas then removed under reduced pressure and the crude product wasdissolved in diethyl ether before filtration on celite to removedinsoluble iodic acid. The filtrate was then concentrated before washing2 times with saturated solution (30 mL of each) of Na₂S₂O₃, NaHCO₃ anddistilled water. Finally, the organic layer was dried (MgSO₄), filteredon celite and the solvent was evaporated to dryness to obtain a yellowliquid 2. M_(n (NMR))=5 300 g·mol⁻¹, M_(n (SEC))=5 750 g·mol⁻¹, Ð=1.9,yield: 90%.

1.2.2. Synthesis of Hydroxy-4 Telechelic Cis-1,4-polybutadiene (3,PB—OH₄), Compound of Formula (IV) of the Invention

ATPB 2 (1.71 g, 0.68 mmol aldehyde) dissolved in 8.5 mL of dry THF and 3eq of DEA (21.5 mg, 2.04 mmol) were mixed and stirred at 40° C. during 2h under inert atmosphere. 3 eq of NaBH(OAc)₃ (433 mg, 2.04 mmol) and 1.2eq of acetic acid were added to the solution and stirred at 40° C.overnight under inert atmosphere. After concentration, the product waspurified by precipitation/dissolution in methanol/DCM several times anddried under vacuum to obtain a colorless liquid 3. Yield=88%.

1.2.3. Synthesis of Furan-4 Telechelic Cis-1,4-polybutadiene (4,PB-fur₄), Precursors of Formula (I) of the Invention

PB—OH₄ 3 (1.37 g, 1.09 mmol hydroxyl groups) was dissolved in 6.5 mL ofdry DCM. 1.5 eq of furan-NCO (176 μl, 1.64 mmol) and 5% mol of DBTDL (32μl, 55 μmol) were added to the solution and stirred at 40° C. during 6 hunder inert atmosphere. After concentration, the product was purified byprecipitation/dissolution in methanol/DCM several times and dried invacuum to obtain a brown liquid 4. Yield=91%.

1.2.4 Synthesis of Furan-4 Telechelic Cis-1,4-polybutadienes of Formula(I) with Various Chain Lengths

In order to synthesize precursors of formula (I) with different chainlengths, aldehyde telechelic polybutadiene 2 (ATPB) were first preparedby the controlled degradation of high molar mass cis-1,4-PB 1 by varyingthe epoxidation rate with mCPBA followed by the oxidative scission ofepoxides with periodic acid.

To study the effect of the chain length, fives molar masses were focusedbetween 5 000 and 19 000 g·mol⁻¹. Results are shown in Table 1.

The aldehyde functions can be easily observed on ¹H NMR spectra with asignal at δ=9.77 ppm that allows to calculate molar masses (see FIG.1A). Molar masses were also determined by SEC and the obtained valuesare very close to the theoretical like those calculated by NMRconfirming the good control of the degradation.

TABLE 1 Chemical characteristics of the polymers synthesized Mn thEpoxydation Mn_(NMR) ⁽¹⁾ Mn_(SEC) ⁽²⁾ f (—OH)⁽³⁾ f (-furan)⁽³⁾ Name g ·mol⁻¹ rate (%) g · mol⁻¹ DP_(NMR) g · mol⁻¹ Ð_(SEC) ⁽²⁾ PB-OH PB-furan 5 kg/mol  5 700 2.10  5 300 97  5 750 1.95 3.9 4.0  9 kg/mol  9 2001.20  8 800 160 12 000 1.64 4.0 4.0 13 kg/mol 11 700 0.91 13 300 246 15800 1.58 4.0 3.9 16 kg/mol 16 500 0.63 16 000 296 20 000 1.85 4.0 3.9 19kg/mol 19 000 0.53 19 000 352 23 000 1.68 3.9 4.0 ⁽¹⁾Calculated by usingthe signal proton of the aldehyde at 9.77 ppm and the proton signal ofthe butadiene units at 5.38 ppm. ⁽²⁾Molar masses and dispersities werecalculated on a SEC calibrated with polyisoprene standards.⁽³⁾Functionality in hydroxy and furan group were calculated by NMR.

Hydroxy telechelic polybutadienes 3 were prepared by reductive aminationof aldehydes group of ATPB 2 with an excess of diethanolamine (DEA) inthe presence of NaBH(OAc)₃ to end up with an hydroxy functionality of 4.The ¹H NMR analysis of the products showed the complete disappearance ofthe aldehyde signal (δ=9.77 ppm) and the appearance of a signalcorresponding to the N—CH₂— at 2.7 ppm indicating a total conversioninto amine (see FIG. 1B). It could be considered, due to the totalconversion of the aldehydes, a theoretical hydroxy functionality of 4.The calculated functionality by the appearance of the new signalcorresponding to the linked DEA at 2.80 and 3.72 ppm confirming thetotal conversion of the aldehyde (Table 1).

The furan-functionalized telechelic polybutadiene precursors 4 (PB-Fur₄)were synthesized from PB—OH₄ by reacting this latter with furan-NCO inthe presence of dibutyltin dilaurate at 40° C.

The ¹H NMR of the products showed all the expected signals correspondingto PB-Fur₄: shift of the HO—CH₂— from 3.72 ppm to 4.12 ppm (see FIG. 1C)and appearance of the furan signal —CH₂—NCO at 4.31 ppm allowed toconfirm the full conversion of hydroxy groups into urethane functions.The calculated furan group functionality is very close to the onecalculated at the PB—OH₄ step and is equal or near to 4 as shown inTable 1.

SEC analysis of the different samples has been performed and theyconfirmed the molar masses values calculated by NMR (Table 1). Besides,elution profiles of the 9 000 g·mol⁻¹ series for example show asuperimposition of the different samples having different chain-ends(see FIG. 2) confirming that no side reactions (coupling andcross-linking) occurs during the chain-end modification steps.

Example 2: Preparation and Characterization of Polybutadiene Films,Polymers According to the Invention

A—Materials and Methods

1. Preparation of Polybutadiene Films

1 g of PB-fur₄ 4 (1 g, DP-93, 796 μmol of furan) was dissolved in 1 mLof CHCl₃ and mixed with 0.5 eq of bis-maleimide (150 mg, 398 μmol)dissolved in 0.5 mL of CHCl₃. The mixture is heated at 60° C. for 10 minin a closed glassware and deposited in a Teflon mold. It is then waited24 h for solvent evaporation and completely dryness was obtained undervacuum for an extra 24 h to obtain a transparent film without airbubbles.

2. Remolding of the Films

All the pieces of strips used for DMA and tensile tests analyses wereput into a hermetic closed pressure resistant glassware (1 g in 1.5 mLof CHCl₃) and heated at 120° C. for 10 minutes. After 5 minutes at roomtemperature, the liquid solution is deposited in a Teflon mold beforewaiting for 24 h for solvent evaporation and it was completely driedunder vacuum for 24 h to obtain a transparent film without air bubbles.

3. Characterization

Liquid-state ¹H NMR and ¹³C NMR spectra were recorded at 298 K on aBruker Avance 400 spectrometer operating at 400 MHz and 100 MHzrespectively in appropriate deuterated solvents.

Polymer molar masses were determined by size exclusion chromatography(SEC) using tetrahydrofuran (THF) as the eluent (THF with 250 ppm ofButylated hydroxytoluene as inhibitor, Aldrich). Measurements in THFwere performed on a Waters pump equipped with Waters RI detector andWyatt Light Scattering detector. The separation is achieved on threeTosoh TSK gel columns (300×7.8 mm) G5000 HXL, G6000 HXL and a MultiporeHXL with an exclusion limits from 500 to 40 000 000 g/mol, at flow rateof 1 mL/min. The injected volume was 100 μL. Columns' temperature washeld at 40° C. Molar masses were evaluated with polyisoprene standardscalibration. Data were processed with Astra software from Wyatt.

Thermo-gravimetric measurements (TGA) of polybutadiene polymer samples(≈12 mg) were performed on a TA Instruments Q500 from room temperatureto 600° C. with a heating rate of 10° C.·min⁻¹. The analyses wereinvestigated under nitrogen atmosphere with platinum pans.

Differential scanning calorimetry (DSC) measurements of polybutadienepolymer samples (≈10 mg) were performed using a DSC Q100 LN₂ apparatusfrom TA Instruments with a heating and cooling ramp of 10° C.·min⁻¹. Thesamples were first heated from 25° C. to 80° C. and held at 80° C. for10 min in order to eliminate the residual solvent, then cooled to −150°C. and finally heated to 200° C. The analyses were carried out in ahelium atmosphere with aluminum pans.

A TA Instrument RSA3 was used to study dynamic mechanical properties ofpolybutadiene polymer samples. The samples were analyzed under nitrogenatmosphere from −105° C. to 200° C. at a heating rate of 4° C.·min⁻¹.The measurements were performed in tensile mode at a frequency of 1 Hz,an initial static force of 0.1 N, and strain sweep of 0.3%.

Fourier transform infrared (FTIR) spectra were recorded on a BrukerVERTEX 70 instrument (4 cm⁻¹ resolution, 32 scans, DLaTGS MIR) equippedwith a Pike GladiATR plate (diamond crystal) for attenuated totalreflectance (ATR) at room temperature.

B—Results

1. Remolding of the Cross-Linked Polybutadiene Polymer of the Invention

Films were prepared by mixing the PB-Fur₄ dissolved in CHCl₃ withstoichiometric quantity of bis-maleimide. After evaporation of thesolvent and drying under vacuum, transparent film without air bubbleswere obtained (see FIG. 3). Strips with width of 5 mm, length of 25 mmand thickness between 0.4 and 0.7 mm were prepared by cutting the filmfor the different mechanical and thermo mechanical analysis.

Dissolution tests of the reversible network formed after addition ofbis-maleimide were thus carried out. FIG. 3 shows the efficientdissolution of the network obtained in chloroform. In FIG. 3, the filmobtained after the first molding is represented on the second picture(from right to left); strips cut from the film and used for the DMA andtensile tests are on the third one; dissolution of the used and breakstrips in a closed glassware in chloroform at 120° C. are on the fourthpicture; finally the new film formed from the used strips is the same asin the second picture.

2. Thermal Properties Analysis

Differential Scanning Calorimetry Analysis.

DSC analysis revealed an identical T_(g) around −103° C. for eachpolymer samples regardless the chain length and the chain-endmodification of the polybutadiene precursors.

Comparison of the cross-linked PB with different chain length of the PBprecursor is shown on FIG. 4A. Two endothermic peaks at 110 and 140° C.and one exothermic peak beginning at 160° C. were observed. RetroDiels-Alder reaction (rDA) is endothermic and exhibit two transitions:one for the endo-adduct and one for the exo-adduct. The exo-adduct,thermally more stable occurs at higher temperature as shown on thecurves. Comparison of the 9 000 g·mol⁻¹ intermediates series indicatethat the two endothermic peaks appear only when the polybutadiene iscross-linked confirming the occurrence of rDA reaction (see FIG. 4B).

Analyses of the recycled elastomer show the same results: the twoendothermic peaks corresponding to the rDA occur at the same temperaturefor the first molding and the recycled one. This information indicatesthat the thermal transitions are not affected by the re-molding of thepolymer of the invention.

Crystallization and melting points of the cis-1,4-polybutadiene areknown to be around −40° C. and −10° C. respectively.

The aldehyde telechelic polybutadiene with chain length of 9 000 g·mol⁻¹was able to crystallize like the hydroxy and furan homologues (FIG. 4B).However, the intensity of the melting peaks located at −8° C. decreasessignificantly at each step of the PB modifications until a completedisappearance for the crosslinked one. An increase of the sterichindrance of the chain-end could prevent the polymer to crystallizeleading to a decrease of the melting peak intensity. Besides as shown inFIG. 4A, only the crosslinked elastomer with a PB precursor of 19 000g·mol⁻¹ crystallizes. This phenomenon could be attributed to theincapacity for the shorter chain to crystallize due to the entanglementinduced by the cross-linking.

Thermo Gravimetric Analysis.

When all the crosslinked PB (polymers of the invention) are analyzed byTGA, higher weight loss is observed at 300° C. for lower chain length.The 150 kg·mol⁻¹ PB exhibited a loss of 0.5% whereas the loss for the19, 9 and 5 kg·mol⁻¹ polymer was equal to 3.5, 6.8 and 12.9%respectively (see FIG. 5A). This could be attributed to the degradationof the furan ring. Indeed, when the ratio butadiene units/furandecreases (shorter chain), the mass content of furan is higherexplaining the bigger weight loss. To confirm the furan degradationinvolvement at 300° C., curves of 9 000 g·mol⁻¹ intermediate series werecompared, the weight loss at 300° C. appear only at the PB-Fur₄ statewith an equivalent weight loss than crosslinked (see FIG. 5B).

Dynamic Mechanical Analysis.

DMA analysis was further applied in tensile mode in order to measure theproperties of the crosslinked PB (polymers of the invention). In FIGS.6A and 6B, solid lines represent the first molding of the polymerwhereas the dash lines are the recycled ones. Moduli of the samples weremeasured during the heating ramp (4° C./min) between −105 to 100° C.after a controlled cooling ramp (4° C./min) from room temperature to−105° C.

The storage modulus (E) shows a relation between the chain length of thePB precursor and the value of the rubbery plateau (see FIG. 6A, (1),solid lines). The higher values of E′ were obtained for the shorterchain. For instance, the modulus at 25° C. increased from 1.4 MPa to11.4 MPa for chain of 19 kg·mol⁻¹ and 5 kg·mol⁻¹ respectively. Thehigher cross-linking density in the shorter chain makes the materialharder and improves the value of the rubbery plateau.

At higher temperature, curves indicate that all of the polymers start tolose their elastic properties at 80° C. This properties drop is actuallydue to the rDA and not to the melting of the chain. Indeed, it is knownthat the melting of a non-crosslinked elastomer is dependent on thechain length, which is not the case of the present invention. Moreover,in the literature it is mentioned that rDA started to occur at 90-100°C. depending on the system. The observation of property loses at 70-80°C. in DMA analysis is thus due to the tensile mode who adds anadditional strength promoting the rDA.

Loss factor (Tan 6) curves shows, like in DSC analysis an identicalT_(g) around −90° C. regardless the chain length (FIG. 6B).

Recyclability of the polymer was then evaluated. Used strips from thedifferent mechanical analyses were re-dissolved to make a new molding asexplained above. DMA results were reported in dash line on FIGS. 6A and6B. It can be noticed that the second molding does not affect themechanical properties of the cross-linked materials. Indeed, curves fromthe first and second molding overlap perfectly showing the excellentrecyclability of the elastomer. Finally, as observed previously in DSCanalysis, only the longest chain crystallized in DMA.

Tensile Test

Tensile tests were performed to study the chain length effect on themechanical properties. On FIG. 7, the median stress-strain curves of thecross-linked PB after the first molding (solid lines) and remolding(dash lines) can be observed. The tensile strength, the young's modulusand the elongation at break were determined and averaged over fourmeasurements. Results are summarized in Table 2.

TABLE 2 Mechanical properties of the PB in function of the chain length.Young modulus Stress at break Strain at break Elastic modulus Cycle(MPa) (MPa) (%) at 25° C. (MPa)  5 kg/mol First 9.64 ± 0.67 4.8 ± 0.7130 ± 19 11.40 Second 9.58 ± 1.40 4.6 ± 0.4 126 ± 18 12.20  9 kg/molFirst 3.50 ± 0.40 2.8 ± 0.5 160 ± 31 5.20 Second 3.06 ± 0.15 2.9 ± 0.3170 ± 19 4.01 13 kg/mol First 1.41 ± 0.04 2.3 ± 0.3 337 ± 15 2.42 Second1.34 ± 0.04 2.7 ± 0.1 398 ± 15 2.46 16 kg/mol First 0.98 ± 0.05 2.3 ±0.2 421 ± 48 1.62 Second 0.96 ± 0.11 1.4 ± 0.2 380 ± 40 1.56 19 kg/molFirst 0.76 ± 0.16 1.7 ± 0.3 450 ± 75 1.39 Second 0.84 ± 0.09 1.6 ± 0.3375 ± 14 1.33

Recyclability of the polymer was again tested in tensile mode (dashedlines see FIG. 7). An excellent reproducibility in term of youngmodulus, elongation and maximum stress at break was observed. Theseresults are in agreement with the ones obtained in DMA showing theexcellent recyclability of the polymer of the invention showing nomechanical properties loses after remolding.

Recyclability Properties of the Cross-Linked Polybutadiene

To go further in the investigation of the recyclability, thepolybutadiene with a chain length of 13 000 g·mol⁻¹ was chosen toevaluate recyclability over 5 cycles. The process of remolding was thesame as described previously. Curves of the elastic modulus obtained byDMA of the 5 cycles of the recycled polybutadiene were represented onFIG. 8. DMA analyses clearly show that the curves of each sample arenearly superimposed.

These results indicate that the value of the elastic plateau E′, the Tgand the temperature of rDA are not affected by the remolding showingthat the polymer of the invention is really stable after heating andstretching treatment. Tensile tests confirmed the results obtained byDMA (see FIG. 9). The values of young modulus, maximum stress and strainat break are not affected after 5 cycles of recyclability.

In conclusion, the obtained polymer when cross-linked has the propertiesof an elastomeric network whereas when heated, it becomes aliquid/viscous solution which can be remolded at least 5 times withoutproperties loss.

Example 3: Effect of the Cross-Linking Agent Quantity on the Polymer ofthe Invention Properties (Polybutadiene Elastomer)

Samples with chain length of 9 000 and 16 000 g·mol⁻¹ were selected. Themolar ratio of maleimide vs the furan groups were 1, 0.75 and 0.50equivalents. DMA analysis (see FIG. 10) showed that the elastic modulusdecreased with the cross-linking density. Indeed, the modulus E′ isequal to 5.2, 3.2 and 0.8 MPa for a cross-linking density of 1, 0.75 and0.50 respectively for the 9 000 g·mol⁻¹ series. Same behavior can beobserved on the 16 000 g·mol⁻¹ series, the value of the elastic modulusdecreased with the cross-linking density.

Tensile tests were also carried out. Similar trends than for DMA wereobserved. Young's modulus for the 9 000 g·mol⁻¹ series went from 3.1 to0.6 MPa and the maximum stress at break went from 2.9 and 0.7 MPa with across-linking density going from 1 to 0.50. Comparable results wereobtained on the series of 16 000 g·mol⁻¹ (see FIG. 11).

Surprisingly, strain at break is not affected by the cross-linkingdensity; it is seems to be only affected by the chain length asmentioned above. Indeed, strain at break is around 180% and 400% for theseries of 9 000 and 16 000 g·mol⁻¹ respectively whatever thecross-linking density.

Example 4: Synthesis of Precursors of Formula (I) According to theInvention

The compound 4′, corresponding to a precursor of formula (I) of theinvention, is prepared according to the following scheme 2:

High molar mass cis-1,4-polyisoprene (5.42 g) was first epoxidized withmCPBA (1.63 mmol) dissolved in 10 mL of THF in 190 mL of THF at 0° C.After 2 h of reaction at room temperature, periodic acid (1.05 eq.compared to mCPBA, 1.71 mmol) dissolved in 10 mL of THF were addeddropwise and stirred during 2 h at room temperature. The solvent wasthen removed under reduced pressure and the crude product was dissolvedin diethyl ether before filtration on celite to removed insoluble iodicacid. The filtrate was then concentrated before washing 2 times withsaturated solution (30 mL of each) of Na₂S₂O₃, NaHCO₃ and distilledwater. Finally, the organic layer was dried (MgSO₄), filtered on celiteand the solvent was evaporated to dryness to obtain 1′. M_(n (NMR))=500g·mol⁻¹.

1′ (3.50 g) dissolved in 14 mL of dry THF and 3 eq of DEA (234 mg) weremixed and stirred at 40° C. during 2 h under inert atmosphere. 3 eq ofNaBH(OAc)₃ (475 mg) and 1.2 molar eq of acetic acid were added to thesolution and stirred at 40° C. overnight under inert atmosphere. Afterconcentration, the product was purified by precipitation/dissolution inmethanol/DCM several times and dried under vacuum to obtain 2′.

2′ (1.23 g) was dissolved in 15 mL of dry THF. 50 mg NaBH₄ were added tothe solution and stirred at 60° C. during 10 h under inert atmosphere.After concentration, the product was purified byprecipitation/dissolution in methanol/DCM several times and dry invacuum to obtain 3′.

3′ (0.949 g) was dissolved in 10 mL of dry THF. 79 μl offuran-isocyanate and 18 μl of DBTDL were added to the solution andstirred at 60° C. during 10 h under inert atmosphere. Afterconcentration, the product was purified by precipitation/dissolution inmethanol/DCM several times and dry in vacuum to obtain 4′.

The invention claimed is:
 1. A compound having the following formula(I):

wherein: n is an integer comprised between 10 and 2,000; R_(a) isselected from the group consisting of: H, linear or branched(C₁-C₅)alkyl, and halogen atom; A comprises at least one repeating unit(U) having the formula (U1) or (U2):

with R_(a) being as defined above and R_(a″) being selected from thegroup consisting of H, —CH═CH₂, and —C(═CH₂)(R_(a)), R_(a) being asdefined above; B₁ and B₂, independently of each other, have thefollowing formula (B):

or the following formula (C):

wherein at least one of B₁ and B₂ has the formula (B), wherein: X is: abond or a group of formula —NH—X₁—, wherein X₁ is a linear or branched(C₁-C₅)alkylene group; Y is selected from the linear and branched(C₁-C₅)alkylene groups; Z and Z′ are independently of each other —O— or—NH—; W and W′ are independently of each other selected from the groupconsisting of: —C(═O)—NH—Y′—, —C(═O)—Y′—, and —Y′— groups, Y′representing a linear or branched (C₁-C₅)alkylene group.
 2. The compoundof claim 1, wherein the repeating unit (U) is of formula (U1):

Ra being as defined in claim
 1. 3. The compound of claim 2, wherein Aconsists of repeating units (U).
 4. The compound of claim 2, whereinR_(a) is H or a (C₁-C₅)alkyl group.
 5. The compound of claim 1, whereinA further comprises at least one repeating unit (V) having the followingformula:

wherein: R_(b) is selected from the group consisting of: H, OH,(C₁-C₅)alkyl, and halogen atom; R_(c) is H or an halogen atom, or R_(b)and R_(c) form together with the carbon atom carrying them a —C═CH₂group; R_(d) is selected from the group consisting of: H, OH,—S—C(═O)—R_(g), —S—C(═S)—R_(g), —P(═O)(OR_(g))₂, —B(R_(g))₂,furan-2,5-dionyl, and CX′₂R_(f), X′ being a halogen atom, R_(f) beingselected from the group consisting of halogen atom,CH₃—C(═O)—O—(C₁-C₁₀)alkyl, —P(═O)(Hal)₂ with Hal being an halogen atom,R_(g) being a linear or branched (C₁-C₁₀)alkyl group, or R_(c) and R_(d)form together with the carbon atoms carrying them a (C₃-C₆)cycloalkyl ora 3-6 membered heterocyclyl group; the percentage of the number ofrepeating units (V) being inferior or equal to 50% of the number ofrepeating units (U).
 6. The compound of claim 5, wherein the repeatingunits (V) are identical and are selected from the group consisting of:

wherein R_(b), X′, R_(f), and R_(g) are as defined in claim
 5. 7. Thecompound of claim 5, wherein the repeating units (V) are identical. 8.The compound of claim 1, wherein A consists of repeating units (U). 9.The compound of claim 1, having the following formula (Ia):

wherein n, R_(a), A, X, Y, Z and W are as defined in claim
 1. 10. Thecompound of claim 1, wherein R_(a) is H or a (C₁-C₅)alkyl group.
 11. Thecompound of claim 1, wherein Z is —O— and W is —C(═O)—NH—Y′—.
 12. Thecompound of claim 1, having one of the following formulae:

wherein n is as defined in claim
 1. 13. A process for the preparation ofa compound of formula (I) according to claim 1, comprising the followingsteps: a) a reductive amination step comprising the reaction of analdehyde of formula (II):

with at least one amine of formula (III):

with n, R_(a), A, X, Y, and Z being as defined in claim 1, in order toobtain a compound having the following formula (IV):

with n, R_(a) and A being as defined in claim 1, and wherein B₁′ andB₂′, independently of each other, have the formula (B′):

or form with the carbon atom carrying them a —C═O group, and wherein atleast one of B₁′ and B₂′ is of formula (B′); b) if one of B₁′ and B₂′forms with the carbon atom carrying it a —C═O group, a reduction stepcomprising the reaction of the compound of formula (IV) as defined abovewith a reducing agent, in order to obtain a compound having the formula(IV′):

with n, R_(a) and A being as defined in claim 1, and wherein B₁″ andB₂″, independently of each other, have the formula (B′):

or —OH, and wherein at least one of B₁″ and B₂″ is of formula (B′); c)the reaction of the compound of formula (IV) or (IV′) with at least onefunctionalized furane having the following formula (VI):

wherein W″ is independently chosen from the group consisting of:—Y′—N═C═O, —Y′—C(═O)—Cl, —Y′—C(═O)—OH, —Y′—C(═O), and —Y′-Hal, Y′ beingas defined in claim 1 and Hal being an halogen atom; in order to obtaina compound having the formula (I).
 14. A polymer, obtained by thereaction of a compound of formula (I) as defined in claim 1, with acrosslinking agent comprising at least two maleimidyl groups.
 15. Thepolymer of claim 14, wherein the crosslinking agent has the followingformula (VII):

wherein R is chosen from the group consisting of: a linear or branched(C₁₋₂₀)alkylene; a phenylene; and a phenylene-L-phenylene group, with Lbeing selected from the group consisting of: a bond, (C₁-C₆)alkylene,—O— and —SO₂—.
 16. The polymer of claim 14, wherein the polymer is anelastomer.
 17. The polymer of claim 14, wherein the crosslinking agenthas the following formula (VII):

wherein R is chosen from the group consisting of: a linear or branched(C₁₋₂₀)alkylene, said alkylene being interrupted by one or moreheteroatom(s); a phenylene, said phenylene being substituted by one ormore substituent(s) selected from (C₁-C₁₀)alkyl; and aphenylene-L-phenylene group, with L being selected from the groupconsisting of: a bond, (C₁-C₆)alkylene, —O— and —SO₂—.
 18. The compoundof claim 1, wherein W and W′ are independently of each other selectedfrom the group consisting of: —C(═O)—NH—Y′—, —C(═O)—Y′—, and —Y′—groups, Y′ representing a (C₁-C₃)alkylene group.
 19. The compound ofclaim 1, wherein A further comprises at least one repeating unit (V)having the following formula:

wherein: R_(b) is selected from the group consisting of: H, OH,(C₁-C₅)alkyl, and halogen atom; R_(c) is H or an halogen atom, or R_(b)and R_(c) form together with the carbon atom carrying them a —C═CH₂group; R_(d) is selected from the group consisting of: H, OH,—S—C(═O)—R_(g), —S—C(═S)—R_(g), —P(═O)(OR_(g))₂, —B(R_(g))₂,furan-2,5-dionyl, and CX′₂R_(f), X′ being a halogen atom, R_(f) beingselected from the group consisting of halogen atom,CH₃—C(═O)—O—(C₁-C₁₀)alkyl, —P(═O)(Hal)₂ with Hal being an halogen atom,R_(g) being a linear or branched (C₁-C₁₀)alkyl group, or R_(c) and R_(d)form together with the carbon atoms carrying them a (C₃-C₆)cycloalkyl ora 3-6 membered heterocyclyl group, said cycloalkyl and heterocyclylgroups being substituted; the percentage of the number of repeatingunits (V) being inferior or equal to 50% of the number of repeatingunits (U).
 20. A compound having the following formula (IV):

wherein: n is an integer comprised between 10 and 2,000; R_(a) isselected from the group consisting of: H, linear or branched(C₁-C₅)alkyl, and halogen atom; A comprises at least one repeating unit(U) having the formula (U1) or (U2):

with R_(a) being as defined above and R_(a″) being selected from thegroup consisting of H, —CH═CH₂, and —C(═CH₂)(R_(a)), R_(a) being asdefined above; B₁′ and B₂′, independently of each other, have thefollowing formula (B′):

or form with the carbon atom carrying them a —C═O group, and wherein atleast one of B₁′ and B₂′ is of formula (B′); wherein: X is: a bond or agroup of formula —NH—X₁—, wherein X₁ is a linear or branched(C₁-C₅)alkylene group; Y is selected from the linear and branched(C₁-C₅)alkylene groups; Z is independently of each other —O— or —NH—.